Process of liquefying gases.



G. CLAUDE.. PROCESS l01:' LIQUEFYING GASES. AP1 LIOATION FILED mman, 1903.

Patented Aug. 9, 1910.

J i EV 1 L9 /7 V`gr` j 'the last case the lubrication is automatically assured by the presence of the liquefied gas itself formed in the expansion apparatus, on the contrary in the other case-it is necessary to provide a constant lubrication. For this.

purpose suitable lubricating substances vhad to be found that could be usedat these low temperatures, I Iuse for this purpose the light ethers of Russian or American petroleums, called also gasolenes, etc., and the useof the petroleum oils themselves and of analogous hydrocarbons; the. more volatile products being used forthe lowest temperatures. My trials have proved that tliese substances are perfectly suitable to be used asl lubricants at very low temperatures and ltheir use as such was not known until my agents in the cylinders of steam or com-VV pressed Vair engines.

In the particular case, when the gas treated is air and when its liquefaction has for its object to economically extract its oxygen, this method has the further advantage of yielding a liquid richer in oxygen than air. If-the degree of pressure P to which the air is compressed before entering the expansion motor is near the critical pressure of the air, the temperature O2. to

which it must be reduced by the cooling action of the' exhaust air from the expansion inotor must be near the critical temperature in order to effect the liquefaction of the said compressed air. Hence to effect this liquefaction, the exhaust air from the expansion motor mustbe below the critical temperature o 'f the air, since otherwise the exchange of temperatures between the compressed air and the expanded air would -not result in a reducing of the temperaturev of the compressed air to the'requisite degree.- Since the exhaust air is under a far less pressure than the critical pressure, it is of course' possible to operate the expansion motor so as to expand theairto an-extent suicient to lower its temperature below the critical tempera'- ture without ,involvin any liquefaction of ,the air in the motor itself; in other words according to this invention the air must be expanded sufficiently to reduce its tempera- .ture below the critical temperature but not to the temperature at lwhich it will in its expanded condition liquefy.

It is advantageous to carry out the process with thecompressed air compressed near to its critical pressure, because the heat of 4liquefaction of a gas under a pressure near to its critical pressure is very small, practically nil, and hence a comparatively small extraction of heat from such compressed gas will result in the production of a considerable quantity of liquefied gas. The carrying out of the process with the compressed air compressed to a degree near to its critical A pressure involves of course the expanded air employed to cool it being reduced to a temperature below the critical temperature. In order, however, -to avoid the formation of any liquid inthe expansion motor, the degree of expansion resorted to, although it must be sufiicient to bring the temperature of the expanded air below the critical temperature, must not, as above stated, be suiiicient to bring itto thetcmperature at which the expandedl air would liquefy. When the liquefied air is withdrawn from the apparatus and brought from approximately its y critical pressure to atmospheric pressure, a

. great amount of it willbe vaporized and the remaining liquid will be rich in oxygen. The gaseous mixtures rich in nitrogen will be collected and sent to the exchangers of temratures and reheated to utilize their cold.

ut the process I have'just .described for liquefying gases under a high pressure is not suiiicient to obtain a very good result, if, as it is advantageous to do in practice, a considerable degree of expansion is resorted to. Also since-according to this invention no' liquefaction occurs in the expansion motor, all the cold produced in this motor results in a fall of temperature of the cxpanded .gas which brings down the final temperature of this as to a temperature say O1 much inferior, 1 the expansion is great, to the .liquefaction temperaturek O2 of the compressed gas under the is naturally necessary that 1t should be so, since the quantity of gas liquefied by this method will be produced by the reheating of the expanded gas from the tem erature )1 up to the temperature O2 an consequently'will be so much the greater, the greater is the difference between the temperatures O1 and O2. But since the higher the temperature at which the expansion takes place, the better `is the frigorific yield, and since the liquefaction of the gas under pressure can take place as soon as the temerature of the expanded gas is-slightly beow the temperature O2, it would be advantageous to make use of this circumstance by effecting the whole of the expansion at a temperature near O2. To obtain this result the conditions of the expansion must be modified, since we have seen that in performressure P. -It

ing the expansion in a sin le stagethe tem- Y operation this fall of temperature tovliquefy ia'.

a ossible 565 pressed gas com voe'tgiofi.

perature O to a temperature (l, only slightly e ower than the temperature @2; each oil these expansions is utilized to produce the liquelaction of a portion oit the compressed gas at the pressure l). Each expansion will thus correspond to a slight tall of tei'npera- M] ture from the temperature 0 to the temperature l), followed by a reheating up to the temperature 0, with a simultaneous liquefaction of some of the compressed gas under the pressure P. Under these conditions the w work of the motor or motors .will take place at temperatures whose lowest limit ol `tem` perature is O3, which is nearer to the temperature U, than the temperature is, and,

is. therefore much less low than in the case 2@ `oil .a single expansion followed by a single reheating, the result being that the mechanical and fi-igoriic yield or the machine is notably increased-. A practical way'to realize this principle is to use, for instance, a

'25 series of expansion motors in-which the gas i will be submitted successively, by its expansion, to progressive falls el pressure.. rllhe gas will be obliged in its passage from one motor to the next to go through one ol the` ,au two compartments of a liquei'lier. This lique-- her will be, for instance, similar to a surface condenser, one of its compartments being occupied by the being as l have explained under the highest pressure and without circulation, ut only renewed by the induence of this pressure. lnfitsA assage through the liqueer, the expande gas will be reheatcd up :to about the temperature U, of liquefaction A au ol the-gas under 4the pressure P and conseleuiently it will gojto the following motor'less cool 4and capable ol undergoing expansion :under better conditions.,

' lt may be advantageousinpractice to use 45 as successive' expansion organs,

ders ol" increasing 4dimensions oit a. machinel which will present much analogy with the "compound engines or turbines commonly used as steam engines, each oil the cylinders 50 or expansion chambers being connected to the next by means of a temperature exchanger or liquetier, in which the gas will circulate as l have explainedabove'. Alter its passage in the last expansion organ and o5 inthe last liquelier,

the gas completely ex- --pounded,`.l'oroii ,glit back to the' temperature O2 'willfbe led to .the temperatures-exchanger alter having liqueed all vthe gas under pres- 'fsu-re that couldbe liquefied.. It will travel oo iin-tins exchanger in Van opposite direction to y so as to yield to the latf te'rftlie totality of its ycold and come out oil -the exchanger at the compressed gas Ia temperature as near 'as temperature or thev com'- ing to the exchanger.. ln-

possible to the .advisable to raise the gas to be liqueed, this gas' the cylin- .of the compressed gas. 'in utilizing the celdas every case the compressed gas to be liquelied may be sent directly 'to the liquefier.

taking the supply for the liqueer or lique hers from the pipe of the compressed and cooled gas before" its entrance into the rst expansion organ. ll on the contrary vit is pressure ol liqueaction` over the pressure of admission oil'I the gas to be expanded, a special compartment can be kept in t-he exchanger for the highly compressed gas.. rlliis arrangement is illustrated by way oil example in llig. 3. ln 'this dgure, 32 and 33 represent two inner compartments ot' an exchanger 37 32 is kept for the gas to be expanded, which entering at 2l, under pressure and dry, passes directly, alter being` cooled, to the hrst expansion cylindero el a machine, which l have supposed, by way oit example, to have two expansion cylinders.. 'lhe compartment 33 receives in 22 the highly compressed gas to be liquefied, and which alter being cooled passes by a3 into the compartments 26 and 27 ol the liquefiers 2l and 25 in which it is liquehed. ltis drawn od' in the liquid state by the cocks 30 and 31. f 'lhe vapor formed during'the drawing ed' of the liquefied gas and its exposure "to atmospheric pressure maybecollected and added to the exhaust gas ilrom the last expansion cylinder to give up its cold in the liquefier 25 and in the exchanger 37, The compressed gas comes as have said, by 38 to the first expansion cylinder iii which it is partially expanded, becoming colder. nlt then passes by d1 to the second liquetier 25 and dows by l2 into the compartment '3d ol the exchanger 37. l have also found means to'realize the advantages ot the expansion at a less low temperature, in the case ol a' single expansion it is produced, dui'- ing the expansion itself, to liquefy the gas under pressure. This last method is theoretically the best as the lexpansion is .then

isothermic, taking placev at the theoretical.

temperature or' liqueaction 0,. 'lo realize this in practice, the surfaces of contact vbetween thegas under pressure and the gas to be liepietied must be developed as much as possible, the `gas under pressure surrounding the expansion chamber? or being surrounded by it. vl4`ig. 2 gives an illustration ofthis method.' ln Vthis ligure the horizontal expansion cylinder 10 has a double wall ll--l2 forming a chamber 13. -"l'he surfaces ol contact between the compressed gas Vand This means consists 'llti ico , rounding air.

the expansion organs, are lubricated, whenV the gas being expanded is further increased necessary, in a constant manner, by means of petroleum ether, or analogous substances. When the gas liquefied under pressure, more or less near to its critical pressure, is brought under a lower pressure, there is naturally an abundant boiling, the main cause of coolingV -the liquid to its normal temperature under this lower pressure, being in this case the small amount of work done by the vaporized gas against the pressure in the receptacle where it is received. l have found a process to diminish this vaporization, when it is objectionable. It consists in cooling the liquefied gas before drawing it oli', down to atemperature near to the normal temperature of the liqueied gas, under the pressure at which it is drawn olf. This supercooling can be realized to a certain extent, simply by increasing the length of the liquefiers. This will allow the liquid formed in the front part of the liquefiers to remain in contact with the exhaust gas supplied to the liquefier, vfor a certain time, until it -reaches'the extractor and before any reheating of the exhaust gas. In this way advantage is taken for the cooling of the liquid of a portion of the necessary difference ofk temperature between the liquefaction temperature 02 and -the temperature O3 of each partial expansion. But in this particular case, as the very principle. of my process consists in diminishing as much as possible this diii'erence,'it is preferable to make use of another supply of cold and to use for lcoolingthe liquld the exhaust gas of a special expansion motor. This motor will be suppliedby a portion of the compressed gas to be expanded, but the expansion in it will be com lete instead of only artial. A great .fa of temperature will t us. be produced; therefore, a final temperature much lower" than O3. After having cooled the liquid, which can then be drawn of without eatvaporization, the exhaust gas commg rom this machine will finish its course together with the gas comingfrom the other machines. Figl` shows by .way of example the application of this method to the cooling o the'liqui'd air formed in the li uefiers 51 and 52, according to the resent escripy l'tiongjthe air liquefied in t e liquefier 51 passes by the dpipe'54 into the inner compartment of liquefier 52' and together with the air liquefied in this compartment passes to the'lower end thereof where it is further cooled by the exhaust air from the motor 55. This air after having played its part in cooling the liquid passes in 52 along with the exhaust air from the last expansion cylinder of the compound expansion engine already described, and after being utilized in this last liqueer 52 it passes to the main exchanger 56. As regards the motor 55, it is supplied by a branch 57%58, of the compressed and cool air to be expanded, but this air undergoes in 55 a complete .,and not a partial expansion. The liquid air, very cold, 1s extracted by a cock 59.

What I claim is:

l. The process of .liquefying gas which consists in cooling and compressing the gas near to its critical pressure, expanding some of said compressed and cooled gas with production of external recoverable work suliciently to reduce its temperature below its critical temperature but not down to its liquefaction temperature, causing this expanded gas to be partially reheated by liquefying some of the gas cooled and com ressed near to its critical pressure, and lina y causing this expanded and partially reheated gas to cool the compressed gas to be expanded and to be' liquefied by circulating in the opposite direction to it. l

2. The process of liquefying gas which consists in cooling and compressing the gas near to its critical pressure, partially expanding some of said compressed and cooled gas with production of external recoverable work suciently toreduce its temperature below its critical temperature but not down to its liquefaction temperature, causin this partially expanded gas to be parta y reheated by liqueying some of its gas, cooled and compressed near to its critical pressure 'submittingthis partially reheated gas to a further and complete expansion with roduction of external recoverable work w 'ch again reduces its temperature below its critical temperature but not down to its liquefaction temperature, reheatin this completely expanded gas firstly by ique ing a further quantity of the gas cooled an compressed near to' its critical pressure and finally byA cooling the gas to be compressed and the gas to be expanded bycirculating.A

1n the opposite direction to the latter.

3. The process of liquefying' air which consists in' cooling and compressing the air near to its critical pressure, partially expanding some of said compressed and cooled air ,in a motor doing external work suiiciently to reduce its temperature below its critical .temperature but not down to its li uefaction temperature, causing this partial expanded air to be partially reheated by iqueying some of the air, cooled and compressed near to its critical pressure submitting this partially reheated air to a further and complete expansion in a motor doing external work which again reduces its temperature' below its critical temperature but not down to its liquefaction temperature, reheating this completely expanded air firstly by liquefying a further quantity of air cooled and compressed near to its critical pressure and finally by cooling the air to be compressed andthe air to be expanded by circulating inthe opposite direction to the latter.

1l. The process of liquefying a gas which l consists in cooling and compressing the gas near to its critical pressure compressing another gas, cooling it, expanding said compressed and cooled gas with reduction of external yrecoverable work sufiiciently to reduce its temperature below the critical temperature oiz the gas intended to be liquefied but not down to its own liquefaetion temperature, causing this expanded gas to be partially reheated by liquefying the gas intended to be liquefied and previously compressed and cooled, and finally causing the expanded and partially reheated gas to cool the gas to be expanded and the gas to be liquefied by circulating in the opposite direction to them.

5. The process of liquefying a gas which lconsists in cooling and compressing the gas near to its critical pressure compressing another gas, cooling it, partially expanding said compressed and cooled gas with prod uction of external recoverable work suiciently to reduce its temperature below the critical temperature of the gas intended to be liquefied but not down to its own liquefactlon temperature, causing this partially expanded gas to be partially reheated by liquefyinga portion of the gas intended to be liquefied and previously compressed and cooled, submitting the partially reheated gas to a further and complete expansion with production of external recoverable work which again reduces its temperature-"below the critical temperature of the gas intended to be liquefied but not down to its own liquefaction temperature, pletely expanded gas' firstly by liquefying another portion of the gas intended to be liquefied and previously compressed and cooled, and finally by cooling the gas to be expanded and the gas to be liquefied by circulating in the op osite direction to them.

6. The process o? liquefying a gas which consists in compressing another gas, cooling it, expanding said compressed and cooled .reheating this comgas with production of external recoverable work at a temperature as near as possible to the temperature of the liquefaction of the gas intended to be liquefied4 and previously compressed and cooled, liquefying the latter by keeping it in as long and as extensive indirect contact as possible with the expanding gas in order to absorb thecold as it is produced by ther expansion, and causing the expanded gas to cool the gas to be liquefied and the gas to be expanded.

7. In a process oi' liquefying gas cooled and con'ipressed near Ato its critical pressure, by expanding some of it with production of external recoverable work sufficiently to reduce its temperature below the critical temperature but not down-to its Iliquefaction temperature, causing this expanded gas to be partially reheated by liquefying some of the gas cooled and compressed near to its critical pressure, and afterward causing this expanded and partially reheated gas te cool the compressed gas to be liquefied, cooling the liquid under pressure so obtained, so as to avoid its excessive evaporation when drawing it ofi' under a lower pressure, by `causing it to fiow for some distance in indirect contact with gas at a lower temperature than that of the liquid under pres-V sure.

8. In a process of liquefying gas cooled and compressed near to its critical pressure, by expanding some of it with the production of externalvrecoverable work sufliciently to reduce its temperature below its critical temperature, but not down to its liquefaction temperature, causing this expanded gas to be partially reheated by liquefying some of the gas cooled and compressed near to its critical pressure,and afterward causing this expanded and partially reheated gas to cool the compressed gas to be liquefied, cooling the liquid under pressure so obtained, so as to avoid its excessive evaporation when drawing it off under a lower pressure,by subjecting a portion of the compressed and cooled gas to a complete expansion with the production of external work, and bringing this expanded gas into indirect contact with the aforesaid liquid before its withdrawal.

In testimony that I claim the foregoing I have hereunto set my hand this eighth day of January 1903.

GEORGES CLAUDE.

4 Witnesses:`

EMILE CoMI-IOUD, AUGUSTUS E. INGRA'M. 

